Vertical Distribution and Source Analysis of Metals in Bohai Bay Based on Sedimentary Cores

 In this study, we investigated the vertical distribution of metals in Bohai Bay and analyzed the changes in heavy metal sources before and after the construction of a dam in 1970. This was accomplished by measuring grain size as well as the concentrations of major metals and heavy metals (Al, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Zn, Cd, Pb, Sb, Hg) within coastal column sediments located in western Bohai Bay. The results indicate that the sediment is predominantly composed of silt and clay with particle sizes ranging from 4.83 to 6.69 micrometers. Factor analysis and normalization techniques reveal that following the completion of moisture-proof gates for rivers discharging into the sea within the Haihe River Basin during this period—specifically from the late 1960s to early 1970s—the metal concentrations in marine areas near estuaries were primarily influenced by natural geochemical processes. Nevertheless, anthropogenic activities such as industrial emissions continue to represent significant pollution sources. The findings indicate that the accumulation characteristics of metals in various sedimentary environments exhibit significant temporal and spatial variations.